1. Field of the Invention
This invention pertains generally to a method and apparatus for displaying a selected geographic area on a video display and more specifically to the providing of a user-friendly graphical interface that defines a template and builds an aircraft optical disk image (AODI) from the data available within the given template's boundaries.
2. Description of the Related Art
The current techniques for defining and building an aircraft optical disk image (AODI) utilizes a specialized computer system to define and build map coverages. An AODI is an image file consisting of several groups, or subdirectories, of map tiles, or segments, that are arranged in hash tables. Each subdirectory is identified in an AODI superdirectory by its map scale and zone, and its starting address.
Rectangles are used to define the bounds of an area of desired coverage. If a nonrectangular area of coverage is desired, the current technique can only approximate the coverage. This is accomplished by using multiple rectangles of varying size. This technique does not provide an accuracy check to verify the exact latitude/longitude or row/column extent of the coverage. The extent of the AODI coverage is estimated by interpolating between the edges of the AODI coverage and the latitude/longitude markings on a base map. Although an approximated outline of the coverage bounds is available utilizing the current techniques, this outline reflects neither missing segments in the data nor does it show individual segments. Further, current techniques are capable of only defining map coverage in non-polar regions (below 51.degree. N and above 51.degree. S).
Present technology is capable of calculating the size of an individual subdirectory of an AODI. However, there is no current capability to determine the complete AODI size before writing the individual subdirectories to the aircraft optical disk (AOD). This reduces the ability to fully utilize all of the AOD space when a margin of error is included in the computations. Neither can polar data be defined, viewed, or created with the current mapstation technology. Although areas of coverage can be deleted or modified using the previously discussed rectangular method, there is no method of precisely adding or deleting individual segments within a coverage.
If two data sources overlap and one of the sources is more current than the other, the current technology does not provide a means for controlling the order in which the data sources are selected for an AODI build. Once entered into a database, the data sources are stagnant and cannot be changed or replaced unless all data sources are relogged into the database. Utilizing current technology, each subdirectory is built, the subdirectory is written to the AOD, and then the subdirectory is erased from a computer hard disk and a new one built. The multiple subdirectories cannot be merged into a single AODI or saved to a computer hard disk.